#pph21-calculator {
  max-width: 400px;
  margin: 2em auto;
  padding: 1.5em;
  border: 1px solid #ddd;
  border-radius: 6px;
  background: #fafafa;
  font-family: sans-serif;
}

#pph21-calculator h1 {
  text-align: center;
  margin-bottom: 1em;
  font-size: 1.5em;
}

#pph21-calculator label {
  display: block;
  margin-bottom: 0.75em;
  font-size: 0.9em;
}

#pph21-calculator input {
  width: 100%;
  padding: 0.5em;
  margin-top: 0.25em;
  box-sizing: border-box;
}

#pph21-calc-btn {
  display: block;
  width: 100%;
  padding: 0.75em;
  margin-top: 1em;
  border: none;
  border-radius: 4px;
  cursor: pointer;
  background: #0073aa;
  color: #fff;
  font-size: 1em;
}

#pph21-result {
  margin-top: 1em;
  font-weight: bold;
  text-align: center;
}

#pph21-explanation {
  margin-top: 1.5em;
  font-size: 0.85em;
  color: #555;
}

/* FAQ box */
.pph21-faq {
  margin-top: 2em;
  padding: 1em;
  background: #fff;
  border: 1px solid #e0e0e0;
  border-radius: 6px;
}
.pph21-faq h3 {
  margin-bottom: 0.75em;
}
.pph21-faq h4 {
  margin: 0.75em 0 0.25em;
  font-size: 1em;
}
.pph21-faq p {
  margin: 0 0 0.75em;
  font-size: 0.9em;
  color: #333;
}